carbon ǀ nitrogen ǀ phosphorus
AirPrex™: Process for Optimization of
Biosolids Treatment with the option of Phosphate
Recovery
July 2015
Contents
• Biological Phosphate-Removal
• Influence of Phosphate onMagnesium-Ammonium-Phosphate (MAP/ Struvite) crystallization
Sludge properties / Sludge dewatering
P- Recovery
• Phosphate precipitation as Struvite
• AirPrex™- Installations References
• Use of Struvite
• Summary and Outlook
Enhanced Biological Phosphate Removal
Aerobic Biological Zone
=
increased PO4 intake
due to the
formation of polyphosphates
Anaerobic Zone / Digester
=
PO4 release
due to the
hydrolysis of polyphosphates
ortho PhosphateOxygen
(Nitrate)
PHA
Glycogene Growth
Energy
Polyphosphate
ortho PhosphateFatty acids
PHA
Glycogene
Electrons
Energy
Poly Phosphate
inner cell structure
Inlet
100 % ~ 1,80 g P/(E*d)
Outlet
10 % ~ 0,18 g P/(E*d)
Waste Activated
Sludge (WAS)
80 % ~ 1,45 g P/(E*d)Primary Sludge
10 % ~ 0,18 g P/(E*d)
Quelle
: U
BA
, 2007
WAS is main
carrierer for
phosphate
Phosphorus flow and –concentrationsin the WWTP
Possible areas for P-Recovery
Primary
Clarification
Aeration Secondary
Clarification
Grit chamber
Inlet Effluent
Grit
Returned WAS
Process water
2
1
Sludge
Sludge liquor
Sludge ash
2
1
Areas for recovery:
Biological Phosphate Removal (Bio-P)
Release of ortho-P
M
Biogas
Dewatering IncinerationDigester3
3
Integration of the AirPrex® Process
Primary
Clarification
Aeration Secondary
Clarification
Grit chamber
Dewatering IncinerationDigester
Inlet Effluent
Grit
Returned WAS
Process water
M
Biogas
AirPrex™
Biological Phosphate Elimination in theWater phase Summary
• Internal recycling of ortho-phosphate (PO4-P)
• Uncontrolled Struvite crystallization and deposits
• Negative influence on the sludge dewatering (lower DS and / or higher Polymer usage)
• High internal P-recycling by sludge liquor
Formation of Magnesium-Ammonium-Phosphate (MAP/Struvite)
Chemical equation:Mg2+ + NH4
+ + HPO42- + 6H2O = MgNH4PO4 * 6H2O + H+
Mg NH4 PO4 6 H2O
Molar weights
[g/mol]:
Struvite: 245
24.3 18.0 95.0 108.0
Share in per cent
[%]:9.9 7.3 39.0 43.8
Mg2+ + NH4+ + H2PO4
- + 6H2O = MgNH4PO4 * 6H2O + 2H+
Mg2+ : 40 mg/L
HCO3- : 2500 mg/L
MAP precipitation area
Mg2+ in solution
PO4-P
7
7,5
8
8,5
9
10 20 30 40 50 60 70 80 90 100 110 120 130 140
ortho-Phosphat [mg/ l]
pH
Struvite
Struvite CrystallisationRelation P-content and pH
Uncontrolled Struvite precipitations
Water absorption by hydrogels
(EPS), shown with polysaccharides,
proteins, etc.
Stabilisation due to phosphates and
increased pH values
Consequence:
Increased water absorption capacity
AND
therefore decreasing sludge dewatering
efficiency (less cake dryness and higher
Polymer consumption)
Influence of Ortho-Phosphates on the water absorption capacities of digested sludge
20
21
22
23
24
25
26
27
10 30 50 70 90 110 130 150
PO4-P Content in the Sludge Water [mg/l]
DS
Dis
ch
arg
e D
ecan
ter
[%]
Influence of the PO4-P concentration on the dry solid content during dewatering
• CO2 stripping by aeration
• Increase of pH to 7.8 – 8.2
• Addition of Magnesium chloride
(MgCl2)
• Growing and sedimentation of
Struvite
• Struvite separation and cleaning
AirPrex® Process for the targeted Struvite precipitation
AirPrex® Process for selective MAP - Precipitation
o Aeration for CO2 stripping andcirculation
o Addition of Magnesiumchloride(MgCl2)
o MAP- crystal growth andsedimentation
o MAP - Separation andMAP - Cleaning
MgCl2
AirPrex® Process for selective MAP - Precipitation
AirPrex® Process for selective MAP - Precipitation
Economic drivers for AirPrex®
1. Increase of cake dryness by appr.
3 to 4% (e.g. 22% 26%)
2. 95% reduction of Ortho-P
concentration in the sludge liquor
3. Elimination / prevention of
crystallization in the entire
sludge- and centrate area
4. Production of Struvite
AirPrex® Process - The perfect location
for maximum savings
AirPrex® Installations & References
The following WWTP already use an AirPrex® System:
Berlin Waßmansdorf (Germany), 1.200.000 P.E. (2010)
Mönchengladbach Neuwerk (Germany), 650.000 P.E. (2010)
Wieden-Echten (Netherlands), 190.000 P.E. (2013)
Amsterdam-West (Waternet, Netherlands), 1.000.000 P.E. (2013)
Uelzen (Germany), 83.000 P.E. (since March 2015)
ASG Salzgitter Nord (Germany), 120.000 P.E. (since April 2015)
Tianjin (China), 1.000.000 P.E. (Start-up Nov. 2015)
Wolfsburg (Germany), 120.000 P.E (Start up July 2016)
Berliner Wasserbetriebe (BWB), Germany
Berlin-Wassmannsdorf WWTP (1,000,000 P.E. or People Equivalent)
Capacity AirPrex®: 2,000 m³/d anaerobically digested (AD) sludge
Struvite production: approx. 2,500 kg/d
Start-up: 2010
AirPrex® Installation Berlin-Wassmannsdorf WWTP (Germany)
Quelle
: A
.Lengem
ann, B
WB
Problem:
uncontrolled Struvite precipitation
AirPrex® Installation Berlin-Wassmannsdorf WWTP (Germany)
Struvite as bulk delivery
Quelle: Berliner Wasserbetriebe, 2013
Struvite packaged for sale to public
AirPrex® Installation Berlin-Wassmannsdorf WWTP (Germany)
Daily Phosphorus Balance of Berlin Wassmannsdorf WWTP
Inlet180.000m³/d
appr. 13 mg/l Ptot
2355 kg Ptot/d2278 kg Pel./d
ScreensGrit Trap Aeration Secondary
Clarifiers
Mixed SludgeStorage Tank
WASThickening
Diges-tion
AirPrex® Reactor
SludgeDewatering(Centrifuges) Dryer
Outlet
77 kg Ptot/dappr. 0,3 mg/l Ptot
PrimaryClarifiers
MgCL2(5 l/m³)
PO4-P 350 mg/l2.000 m³/d 700 kg/d
Incineration
2,9 t MAP in thesludge (54%)367 kg P5 kg P/t DS
2.025 kg Ptotin the ash
PO4-P Outlet<20 mg/l
95% Reduction
MAP Recovery:2,0 t/d=37% of total MAP253 kg P/d = appr. 11% of Pel.(In-/Outlet)
10.04.2016 Andreas Lengemann
57 kg PO4-P Backcharge
2153 kg Ptot
Quelle
: N
iers
verb
and
AirPrex® Installation Moenchengladbach-Neuwerk WWTP (Germany)
DigesterDewatering
AirPrex® Installation Moenchengladbach-Neuwerk WWTP (Germany)
Niersverband, Germany
MG-Neuwerk WWTP (995,000 P.E.)
Capacity AirPrex®: 1,500 m³/d digested sludge
Struvite production: 1,500 kg/d
Start-up: 2009
AirPrex® Installation Moenchengladbach-Neuwerk WWTP (Germany)
AirPrex® ProcessM‘gladbach-Neuwerk Economy
A. Only Bio-P: 3.150.000 € p.a.
B. Bio-P plus AirPrex®: 2.600.000 € p.a.
C. chem. P-Precipiation (FeCl2): 3.200.000 € p.a.
Data
: N
iers
verb
and
2.000.000
2.500.000
3.000.000
3.500.000
4.000.000
4.500.000
20 22 24 26 28 30 32
DS after dewatering (%)
To
tal C
os
ts(D
isp
os
ala
nd
Po
lym
er)
in
[E
uro
/yr]
ß= 1,3
Basis 2005/2006
C. FeCl3- Precipitation
B. Bio-P with AirPrex®
A. Only Bio- P
Reest & Wieden, NL
Echten WWTP (190,000 P.E.)
Capacity AirPrex®: 400 m³/d AD sludge
Struvite production: appr. 500 kg/d
Start-up: 2013
AirPrex® InstallationEchten WWTP (Netherlands)
Waternet, NL
Amsterdam-West WWTP (1,000,000 P.E.)
Capacity AirPrex®: 2,500 m³/d AD sludge
Struvite production: 4,000 – 5,000 kg/d
Start-up: 2014
AirPrex® InstallationAmsterdam WWTP (Netherlands)
Inlet168.000 m³/d
appr. 8 mg/l Ptot
1.561 kg Ptot/d1.426 kg Pel./d
ScreensGrit Trap Aeration Secondary
Clarifiers
WASThickening
(684 m³/d; 47 t DS/d)
Digestion
AirPrex®
Reactor
4,8 t/d MAP Production
SludgeDewatering
(Centrifuges)
Outlet
135 kg Ptot/dappr. 0,8 mg/l Ptot
PrimaryClarifiers
PS Sludge:800 m³/d44 t DS/d
MgCl2(3,5 l/m³)
External Sludge(PS/ WAS Mixture)
600 m³/d; 26 t DS/d
PO4-P Outlet AirPrex®
<30 mg/l(63 kg/d)
MAP Recovery:2,5 t/d = 52% of total MAP315 kg P/d = ~ 22% of Pel.(In-/Outlet)
32 kg PO4-P Backcharge
Mixed SludgeStorage
Tank
1.426 kg/d Ptot
Incineration
2,3 t/d MAP in thesludge (48%)290 kg P/d
1.050 kg Ptotin the ash
PO4-P 300 mg/l2.084 m³/d 625 kg/d
Daily Phosphorus Balance of Amsterdam West WWTP
Uelzen WWTP, Germany (83,000 P.E.)
Capacity AirPrex®: 120 m³/d AD sludge
Struvite production: no MAP recovery
Start-up: April 2015
AirPrex® InstallationUelzen WWTP (Germany)
Salzgitter WWTP, Germany (120,000 P.E.)
Capacity AirPrex®: 240 m³/d AD sludge
Struvite production:
Start-up: July 2015
AirPrex® InstallationSalzgitter WWTP (Germany)
Wolfsburg WWTP, Germany (185,000 P.E.)
Capacity AirPrex®: 280 m³/d AD sludge
Struvite production:
Start-up: November 2015
AirPrex® InstallationWolfsburg WWTP (Germany)
Jing Nan Tianjin WWTP, China (1,000,000 P.E.)
Capacity AirPrex®: 1,608 m³/d AD sludge
Struvite production:
Start-up: Nov. 2015
AirPrex® InstallationJing Nan Tianjin WWTP (China)
Use of Struvite
• Struvite:
By-product with a good use as a fertilizer
• Nutrients have been proven in accordance
with the German law (certified as fertilizer)
low heavy-metal content
slow release of nutrients
(no wash-away effect)
• REACH certified
Summary and Outlook
• The specific phosphate precipitation by Struvite crystallization
(AirPrex®) leads to the following advantages
• Minimize the crystallization potential
• Positive impact on the sludge dewatering by a constant
P-Elimination rate between 90 and 95%
• AirPrex® is an approved and reliable technology with
large-scale references
• Good quality fertilizer as a by-product
Thank you for
your attention
and interest!